CHICAGO (Reuters) - No matter how much the U.S. medical community challenges the suggestion by presidential candidate Michele Bachmann that a vaccine for human papillomavirus (HPV) is dangerous, doctors fear the damage has already been done.

Physicians are bracing for more parents to refuse the HPV vaccine, which protects against the most common cause of cervical cancer, for their daughters.

They say the comments by the Republican candidate will only stoke growing and unfounded fears about a whole class of common immunizations needed to fight disease.

"There are people out there who, because of this kind of misinformation, aren't going to get their daughter immunized," said Dr. Kenneth Alexander, a pediatric infectious disease expert at the University of Chicago Medical Center.

"As a result, there will be more people who die from cervical cancer," Alexander said in a telephone interview.

"There will be repercussions of this comment that will directly impact every provider who takes care of adolescents and young women," Jackson said in a telephone interview.

Bachmann first raised the issue during a Republican presidential debate on Monday as a swipe at Republican rival and Texas Governor Rick Perry, who issued an executive order in 2007 mandating girls get the HPV vaccine as part of a school immunization requirement. The order was later overturned.

In that forum, she questioned the state's authority to force "innocent little 12-year-old girls" to have a "government injection" that was "potentially dangerous."

The following day, she told NBC's "Today" show the story of a woman from Tampa, Florida, who approached her after the debate and said her daughter became "mentally retarded" after getting the Gardasil vaccine made by Merck.

Physician groups including the American Academy of Pediatrics rushed out statements defending the safety of Merck's vaccine and Cervarix made by GlaxoSmithKline, whose most common side effects include a sore arm, a rash and fever.

As a measure of their incredulity over Bachmann's comments, two bioethicists are offering rewards, one of more than $10,000, if she can bring forward the child who suffered irreparable damage.

'THE INTERNET, AND INNUENDO'

Doctors say more than 35 million doses of Gardasil have been administered since it was approved in 2006 and its safety profile has held up. But no amount of proof will suffice for some families, who fear that even a small percentage of children may be harmed.

"I recently had a mother who had cervical cancer who refused the HPV vaccine for her child," Jackson said. "I asked her where she got her information and she said, 'the Internet, and innuendo.'"

That may help explain the slow uptake of the HPV vaccine. According to the Centers for Disease Control and Prevention, only 32 percent of adolescent girls last year had gotten all three shots of the HPV vaccine.

"We've got 12,000 women a year in this country getting cervical cancer. The vaccine could prevent about 70 percent of that," Alexander said.

Vaccine fears have already fueled recent outbreaks of measles, mumps and whooping cough, according to the CDC.

Much of the fear stemmed from a study by Dr. Andrew Wakefield, the now-disgraced British doctor who researchers believe falsified data for a 1998 study which convinced thousands of parents that vaccines are dangerous.

Concerns that vaccines might cause autism have not only caused parents to skip vaccinating their children, but also forced costly reformulations of many vaccines.

Bachmann's suggestion that the HPV vaccine may be linked with "mental retardation" only feeds into those fears.

"What is especially disturbing is you've got organizations like the American Academy of Pediatrics, the Advisory Committee on Immunization Practices, the American Academy of Family Physicians and the American College of Obstetricians and Gynecologists -- every learned medical organization in the country and indeed around the world -- in favor of immunization," Alexander of the University of Chicago said.

Jackson said when presented with information about the HPV vaccine, about 85 percent of families decide to have their child vaccinated, about 12 percent are hesitant, and the rest are "flat-out refusers."

It's the families in that 12 percent she is worried about.

"It's not going to impact the flat-out refusers. I worry it is going to impact this group of vaccine-hesitant families."